Mobile phone networks, like any other network, cannot be operated unless
the location of each associated device is known. That cannot be avoided.
Current mobile phone networks in the UK record location in terms of cell
ID. Cells are defined by base stations, also known as "radio masts" or
"antennae". Each base station has an ID and defines a cell. Assuming that
an omni-directional antenna is used:

In low message traffic areas the cell is a sphere with a radius of
several kilometres.

In high message traffic areas, where there are more base stations,
the radius falls to 150 metres or less.

When a mobile phone associates with a base station, i.e. when there is
at least one blob of signal on the screen, its location can be narrowed
down to the given cell and the mobile phone network operators can detect
the location of the phone accurately to within several kilometres in the
countryside, 150 metres in the city and sometimes better.

The main location-detection technologies being used in the US and Europe
are EOTD and AGPS:

Assisted Global Positioning System is based on GPS.
GPS cannot always be used. It's fine in the desert but it has problems
in cities, in the rain and under leafy trees. AGPS
overcomes some of these problems, works with GSM and CDMA networks and
already offers, so it is claimed by the suppliers, Qualcomm, 5m accuracy.

While EOTD and AGPS approach greater accuracy in location-detection,
other related technologies are overtaking them. 802.11 wireless networks
can provide 5ft accuracy, see for example:

EOTD looks as though it has problems achieving accurate location-detection,
AGPS seems to be well on the way and the possibility of using multi-protocol
mobile phones, incorporating 802.11, looks most promising, given the growing
prevalence of WiFi hotspots.

PS

WiFi hotspots use 802.11, which operates in the unlicensed, free industrial,
scientific and medical bands (ISM), and if hotspots one day achieve
the coverage of mobile phone networks, can we look forward then to using
voice over IP (VoIP) instead of GSM/GPRS/UMTS/CDMA, with their attendant
waveband licence fees, including £22.5bn wasted on 20-year 3G
licences in the UK, and saving money as a result?

PPS

Location-detection accuracy is set to grow. At the same time, people
in the UK remain apparently uninterested in the privacy issues. For
example, the London Congestion Charge scheme incorporates Automatic
Number Plate Recognition software attached to CCTV cameras. While Ken
Livingstone won Worst Public Servant at the 2003
UK Big Brother Awards and Capita won Most Invasive Company,
the scheme has been declared a success and is set to be emulated all
over the UK and overseas.

(The paragraphs above are adapted from a paper produced
in May 2003
(para.4.6). The research has not been updated since then. Many references
in the May 2003 paper have been removed, having disappeared from the web
in the interim.)